Vibrator, oscillator, electronic device, and moving object

ABSTRACT

A MEMS vibrator includes: a substrate; a base portion which is disposed on the substrate; and a plurality of vibration portions which extend in directions different from each other from the base portion. The MEMS vibrator has a curved surface between the adjacent vibration portions.

BACKGROUND

1. Technical Field

The present invention relates to a vibrator, an oscillator provided withthe vibrator, an electronic device, and a moving object.

2. Related Art

An electro-mechanical system structure (for example, a vibrator, afilter, a sensor, or a motor) provided with a mechanically movablestructure which is called a micro electro mechanical system (MEMS)device which is formed by using semiconductor micro fabricationtechnology, is generally known. Among these, compared to an oscillatorand a resonator using quartz crystal or a dielectric in the related art,since a MEMS vibrator is easy to be manufactured by incorporating asemiconductor circuit and advantageous in miniaturization and highfunctionality, the usage range thereof widens.

As representative examples of the MEMS vibrator in the related art, forexample, a comb type vibrator which vibrates in a direction parallel toa substrate surface provided with the vibrator, and, for example, a beamtype vibrator which vibrates in a thickness direction of the substrate,are known. The beam type vibrator is a vibrator which has a fixedelectrode formed on the substrate or the movable electrode separated anddisposed on the substrate, and according to a method of supporting amovable electrode, a cantilevered beam type (clamped-free beam), adouble-end supported beam type (clamped-clamped beam), or a both-endsfree beam type (free-free beam) are known.

In the MEMS vibrator in a cantilevered beam type in JP-A-2012-85085, ina side surface portion of a first electrode provided on a main surfaceof the substrate, a corner of the side surface portion provided on asupporting portion side of a movable second electrode is formedsubstantially perpendicularly. For this reason, it is possible to reducean effect of the variation of a vibration characteristic caused by avariation in an electrode shape, and to obtain a stable vibrationcharacteristic.

However, the MEMS vibrator in JP-A-2012-85085 is advantageous in thatthe size thereof can be reduced since there is one supporting portion.However, since the mass of the supporting portion which fixes thecantilevered beam is small, there is a problem in that a Q valuedeteriorates due to a energy dissipation in which flexural vibration ofthe beam is transmitted through the supporting portion and istransferred to the entire substrate, and in that a high Q value cannotbe obtained and a stable vibration characteristic or a desired vibrationcharacteristic cannot be obtained according to the deterioration of theQ value due to a thermoelastic damping generated by the supportingportion where the stress of flexural vibration is concentrated.

SUMMARY

An advantage of some aspects is to solve at least a part of the problemsdescribed above, and the invention can be implemented as the followingforms or application examples.

Application Example 1

This application example is directed to a vibrator including: asubstrate; a base portion which is disposed on the substrate; and aplurality of vibration portions which extend in directions differentfrom each other from the base portion. The vibrator has a curved surfacebetween the adjacent vibration portions.

According to this application example, by providing the curved surfacebetween the adjacent vibration portions, it is possible to keep apartthe interval of heat sources which causes a thermoelastic damping whichis a cause of the deterioration of a Q value in addition to the energydissipation and is generated between the adjacent vibration portions.For this reason, it is possible to reduce the discharge (thermoelasticdamping) of the heat due to heat conduction between the heat sources,and to obtain a vibrator having a high Q value and a stable vibrationcharacteristic or a desired vibration characteristic.

Application Example 2

This application example is directed a vibrator including: a substrate;a base portion which is disposed on the substrate; and a plurality ofvibration portions which extend in directions different from each otherfrom the base portion. The vibrator has a convex portion between theadjacent vibration portions.

According to this application example, by providing the convex portionbetween the adjacent vibration portions, it is possible to keep apartthe interval of the generated heat sources similarly to a case where thecurved surface is provided. For this reason, it is possible to reducethe discharge (thermoelastic damping) of the heat due to the heatconduction between the heat sources, and to obtain a vibrator having ahigh Q value and a stable vibration characteristic or a desiredvibration characteristic.

Application Example 3

This application example is directed to the vibrator according to theapplication example described above, wherein a width of a tip endportion of the vibration portion is less than that of a root portion ofthe vibration portion.

According to this application example, as the width of the tip endportion of the vibration portion is small, stress at a time of vibrationof the vibration portion is concentrated by a contact portion of thecurved surface or the convex portion which is provided between thevibration portion and the adjacent vibration portion. For this reason,since the thermoelastic damping generated according to the concentrationof the stress can be further reduced, it is possible to obtain avibrator having a high Q value.

Application Example 4

This application example is directed to the vibrator according to theapplication example described above, wherein the vibration portionincludes a root portion provided with a curvature portion, and agradually decreasing portion in which a width becomes smaller toward thetip end portion.

According to this application example, the stress due to the vibrationis further concentrated by the vibration at the contact portion betweenthe root portion provided with the curvature portion and the graduallydecreasing portion in which the width becomes smaller toward the tip endportion. For this reason, since the thermoelastic damping generatedaccording to the concentration of the stress can be further reduced, itis possible to obtain a vibrator having a high Q value.

Application Example 5

This application example is directed to the vibrator according to theapplication example described above, wherein the supporting portionwhich connects the substrate and the base portion is connected to asurface of a side facing the substrate of the base portion.

According to this application example, as the supporting portion isconnected to the surface of the side facing the substrate of the baseportion, it is possible to separate the vibration portion provided inthe base portion from the substrate, and to obtain a vibrator having astable vibration characteristic.

Application Example 6

This application example is directed to the vibrator according to theapplication example described above, wherein the supporting portion isconnected between the adjacent vibration portions.

According to this application example, as the supporting portion isconnected to a nodal point between the adjacent vibration portions, itis possible to reduce the deterioration of the Q value due to the energydissipation, and to obtain a vibrator having a high Q value.

Application Example 7

This application example is directed to the vibrator according to theapplication example described above, wherein a plurality of supportingportions are provided.

According to this application example, as there are plural supportingportions which are connected to the nodal point between the adjacentvibration portions, it is possible to improve impact resistance, and toobtain a vibrator having excellent impact resistance and a high Q value.

Application Example 8

This application example is directed to an oscillator including thevibrator according to the application example described above.

According to this application example, as the vibrator having a high Qvalue is provided, it is possible to provide an oscillator having higherfunctionality.

Application Example 9

This application example is directed to an electronic device includingthe vibrator according to the application example described above.

According to this application example, as the vibrator having a high Qvalue is used as the electronic device, it is possible to provide anelectronic device having higher functionality.

Application Example 10

This application example is directed to a moving object including thevibrator according to the application example described above.

According to this application example, as the vibrator having a high Qvalue is used as the moving object, it is possible to provide a movingobject having higher functionality.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIGS. 1A to 1C are plan views and cross-sectional views of a vibratoraccording to a first embodiment of the invention.

FIGS. 2A and 2B are plan views of an upper electrode of the vibrator foranalyzing heat distribution according to vibration. FIG. 2A is avibrator in the related art. FIG. 2B is the vibrator according to thefirst embodiment of the invention.

FIGS. 3A and 3B are analysis results of the heat distribution accordingto the vibration of the vibrator in the related art. FIG. 3A is aperspective view illustrating the heat distribution. FIG. 3B is anenlarged view of a C part.

FIGS. 4A and 4B are analysis results of the heat distribution accordingto the vibration of the vibrator according to the first embodiment ofthe invention. FIG. 4A is a perspective view illustrating the heatdistribution. FIG. 4B is an enlarged view of a D part.

FIGS. 5A to 5F are flow charts illustrating a manufacturing method ofthe vibrator in order according to the embodiment.

FIGS. 6G to 6K are flow charts illustrating the manufacturing method ofthe vibrator in order according to the embodiment.

FIGS. 7A and 7B are plan views illustrating a vibrator and an example ofa variation of an upper electrode of the vibrator according toModification Example 1.

FIGS. 8A to 8D are plan views illustrating a vibrator and an example ofa variation of an upper electrode according to Modification Example 2.

FIG. 9 is a plan view of the upper electrode of the vibrator accordingto a second embodiment of the invention.

FIG. 10 is a schematic view illustrating a configuration example of anoscillator provided with the vibrator according to the embodiment.

FIG. 11A is a perspective view illustrating a configuration of a mobiletype personal computer as an example of an electronic device. FIG. 11Bis a perspective view illustrating a configuration of a mobile phone asan example of the electronic device.

FIG. 12 is a perspective view illustrating a configuration of a digitalstill camera as an example of the electronic device.

FIG. 13 is a schematic perspective view illustrating a vehicle as anexample of a moving object.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, an embodiment which implements the invention will bedescribed with reference to the drawings. Hereinafter, an embodiment ofthe invention is described, and the invention is not limited thereto. Inaddition, in each drawing below, there is a case where the dimensionsare different from the real dimensions for easy understanding.

Vibrator First Embodiment

First, a MEMS vibrator 100 will be described as a vibrator according toa first embodiment of the invention.

FIG. 1A is a plan view of the MEMS vibrator 100. FIG. 1B is across-sectional view along line A-A in FIG. 1A. FIG. 1C is across-sectional view along line B-B in FIG. 1A.

The MEMS vibrator 100 is an electrostatic beam type vibrator which isprovided with a fixed electrode (lower electrode 10) formed on asubstrate 1 and a movable electrode (upper electrode 20) formed to beseparated from the substrate 1 and the fixed electrode. The movableelectrode is formed to be separated from the substrate 1 and the fixedelectrode as a sacrificing layer stacked on a main surface of thesubstrate 1 and the fixed electrode is etched thereon.

In addition, the sacrificing layer is a layer formed once by an oxidefilm or the like, and is removed by etching after forming a necessarylayer above and below or in the vicinity thereof. As the sacrificinglayer is removed, a necessary gap or a cavity is formed between eachlayer above and below or in the vicinity thereof, and a necessarystructure is formed to be separated.

A configuration of the MEMS vibrator 100 will be described hereinafter.A manufacturing method of the MEMS vibrator 100 will be described in theembodiment which will be described below.

The MEMS vibrator 100 is configured to have the substrate 1, the lowerelectrode 10 (first lower electrode 11, second lower electrode 12)provided on the main surface of the substrate 1, a supporting portion 26which is connected onto the substrate 1 via the lower electrode 10(second lower electrode 12), an upper electrode 20 (integrated with thebase portion 22 and a vibration portion 24) provided with a base portion22 which is connected onto the supporting portion 26, and the like.

On the substrate 1, a silicon substrate is used as a suitable example.On the substrate 1, an oxide film 2 and a nitride film 3 are stacked inorder. In an upper portion of the main surface side (surface of thenitride film 3) of the substrate 1, the lower electrode 10 (first lowerelectrode 11, second lower electrode 12), the supporting portion 26, theupper electrode 20, and the like, are formed.

In addition, here, in a thickness direction of the substrate 1, adirection in which the oxide film 2 and the nitride film 3 are stackedin order on the main surface of the substrate 1 is described as anupward direction.

In the lower electrode 10, the second lower electrode 12 is a fixedelectrode which fixes the supporting portion 26 onto the substrate 1,imparts an electric potential to the upper electrode 20 via thesupporting portion 26, and is formed in an H shape as illustrated inFIG. 1A by patterning a first conductor layer 4 stacked on the nitridefilm 3 by photolithography (including etching processing. The samehereinafter). In addition, the second lower electrode 12 is connectedwith an outer circuit (not illustrated) by wiring 12 a.

The supporting portion 26 is rectangular in a planar view, is overlappedwith the base portion 22 of the upper electrode 20, and is connected tothe surface of the side opposite to the substrate 1 of the base portion22. In addition, the supporting portion 26 is disposed to be overlappedwith the nodal point which is on the base portion 22. Furthermore, thesupporting portion 26 is disposed at a center part of the second lowerelectrode 12. The supporting portion 26 is formed by patterning a secondconductor layer 5 which is stacked on the first conductor layer 4 byphotolithography. In addition, the first conductor layer 4 and thesecond conductor layer 5 use conductive polysilicon as a suitableexample, respectively, but, the embodiment is not limited thereto.

The upper electrode 20 is configured to have the base portion 22 and aplurality of vibration portions 24 which extends in a directiondifferent from each other from the base portion 22. In particular, asillustrated in FIG. 1A, the upper electrode 20 is a movable electrodewhich forms a cross shape with the four vibration portions 24 thatextend from the base portion 22 of the upper electrode 20, is supportedby the supporting portion 26 provided under the base portion 22, and isseparated from the substrate 1. In addition, a curved surface 40 isprovided between the adjacent vibration portions 24, that is, at a partwhere the vibration portions are connected.

The upper electrode 20 is formed by patterning a third conductor layer 6which is stacked on an upper layer of the second conductor layer 5 thatforms the supporting portion 26 and an upper layer of the sacrificinglayer stacked on the first conductor layer 4, by photolithography. Inother words, the upper electrode 20 is integrally formed with the baseportion 22 and the four vibration portions 24. In addition, each centerpart of the second lower electrode 12 and the cross-shaped upperelectrode 20 are overlapped to be substantially matched when thesubstrate 1 is viewed from a planar view, and the two vibration portions24 which extend in a lateral direction (B-B direction) from the baseportion 22 of the upper electrode 20 are disposed to be overlapped withthe second lower electrode 12 (remove a part of a slit S2 which will bedescribed later). In addition, the third conductor layer 6 usesconductive polysilicon as a suitable example, similarly to the firstconductor layer 4 and the second conductor layer 5, but the embodimentis not limited thereto.

In the lower electrode 10, the first lower electrode 11 is a fixedelectrode to which an AC voltage is applied between the first lowerelectrode 11 and the upper electrodes 20 overlapped when the substrate 1is viewed from a planar view, and is formed by patterning the firstconductor layer 4 stacked on the nitride film 3 by photolithography.When FIG. 1A is viewed from a front view, the first lower electrode 11is provided at two locations to be overlapped with the two vibrationportions 24 which extend in a longitudinal direction (A-A direction)from the base portion 22 of the upper electrode 20, and are connectedwith the outer circuit (not illustrated) by wiring 11 a.

The first lower electrode 11 is formed by the first conductor layer 4which is the same layer as the second lower electrode 12. Therefore, thefirst lower electrode 11 is required to be electrically insulatedbetween the first lower electrode 11 and the second lower electrode 12as the fixed electrode which imparts the electric potential to the upperelectrode 20, and each pattern (first lower electrode 11 and secondlower electrode 12) is separated. A step difference (unevenness) of agap for the separation is transferred to the upper electrode 20 which isformed by the third conductor layer 6 stacked via the sacrificing layerstacked on the upper layer of the first conductor layer 4, in an unevenshape. In particular, as illustrated in FIGS. 1A and 1B, in a part of aseparation portion (slit S1) of the pattern, the uneven shape is formedin the upper electrode 20.

In the MEMS vibrator 100, in order to prevent occurrence of a differencein stiffness by the vibration portion 24 which extends in thelongitudinal direction (A-A direction) from the base portion 22 of theupper electrode 20 and the vibration portion 24 which extends in thelateral direction (B-B direction), a dummy slit pattern is provided inthe second lower electrode 12. In particular, like the uneven shapereflected to the two vibration portions 24 in which the slit S1 extendsin the longitudinal direction (A-A direction) of the upper electrode 20,a dummy slit S2 which generates the uneven shape in the two vibrationportions 24 in which the slit S1 extends in the lateral direction (B-Bdirection) of the upper electrode 20, is provided in the second lowerelectrode 12 in which the slit S1 extends in the lateral direction (B-Bdirection) in an area where the upper electrode 20 is overlapped. Inother words, a width (length of B-B direction) of the slit S2 issubstantially the same as a width (length of A-A direction) of the slitS1. The slit S2 is formed so that a distance from a center point of theupper electrode 20 to the slit S2 is substantially the same as thedistance from a center point of the upper electrode 20 to the slit S1,in a planar view.

As the dummy slit S2 is provided in this manner, the upper electrode 20is configured to include an uneven portion. In addition, since the slitS2 is not formed for electrically insulating the second lower electrode12, in a planar view, in the area where both end portions of the slit S2which is not overlapped with the upper electrode 20, the second lowerelectrode 12 continues.

In the configuration, the MEMS vibrator 100 is configured as anelectrostatic vibrator. By the AC voltage applied to between the firstlower electrode 11 and the upper electrode 20 via the wirings 11 a and12 a from the outer circuit, a tip end area of the four vibrationportions 24 of the upper electrode 20 vibrates as an antinode of thevibration. In FIG. 1A, a (+/−) signal illustrates a part which vibratesin a vertical direction (thickness direction of the substrate 1) as theantinode of the vibration, including a phase relationship of thevibration. In addition, the phases of the adjacent vibration portions 24are different from each other. For example, the signal illustrates acase where the +vibration portion 24 moves in the upward direction(direction away from the substrate 1) and the adjacent vibration portion24 moves in the downward direction (direction which approaches thesubstrate 1). In other words, the upper electrode 20 which is themovable electrode vibrates in a direction which intersects a planesurface including the lower electrode 10 (first lower electrode 11,second lower electrode 12) which is the fixed electrode.

Here, the two vibration portions 24 which pinch the base portion 22 andextend in a direction different from the base portion 22, are regardedas a beam in a substantially rectangular shape including the baseportion 22. For this reason, flexural vibration is generated which has adisplacement in the thickness direction of the vibration portion 24 inwhich the base portion 22 vibrates in the downward direction when thetip ends of the two vibration portions 24 vibrate in the upwarddirection. In addition, the adjacent vibration portions 24, the baseportion 22, and the beam which is configured by the two vibrationportions 24 which pinch the base portion 22 and extend in differentdirections from the base portion 22, and generate flexural vibration, inwhich the base portion 22 vibrates in the upward direction when the tipends of the two vibration portions 24 vibrate in the downward direction.For this reason, when the two beams vibrate at the same time, thedisplacement of the base portion 22 in a vertical direction is offsetand the vibration is suppressed, and the area facing a part which isconnected between the center part of the base portion 22 and theadjacent vibration portion 24 is in a state where the vibrationdisplacement rarely exists. By supporting the part, it is possible tomore simply provide the electrostatic beam-shaped MEMS vibrator 100 inwhich the vibration efficiency is higher and the energy dissipation issuppressed.

Next, the Q value of the vibrator is generally determined by the energydissipation which is a vibration energy leakage to the supportingportion, by a loss according to a viscosity of air, or by a loss causedby the heat which is the thermoelastic damping. In addition, the size ofeach loss is different according to the shape of the vibrator, avibration mode, or environment, and it cannot be unconditionally saidwhich has the greatest influence on loss. Here, by vacuum-packaging thevibrator, the influence of the viscosity of air can be ignored. Theenergy dissipation can be reduced by optimizing the structure of thevibrator, and thus, by paying attention to the loss caused by the heatwhich is the thermoelastic damping and investigating a relationshipbetween the structure of the vibrator and the thermoelastic damping, astructure of the vibrator which has low thermoelastic damping and high Qvalue has been considered.

The relationship between the structure of the upper electrode 20 of thevibrator and the thermoelastic damping according to the embodiment willbe described in detail.

FIGS. 2A and 2B are plan views of an upper electrode of the vibrator foranalyzing heat distribution according to vibration. FIG. 2A is avibrator in the related art. FIG. 2B is the vibrator according to thefirst embodiment of the invention. In addition, FIGS. 3A and 3B areanalysis results of the heat distribution according to the vibration ofthe vibrator in the related art, by the finite element method. FIG. 3Ais a perspective view illustrating the heat distribution. FIG. 3B is anenlarged view of a C part in FIG. 3A. FIGS. 4A and 4B are analysisresults of the heat distribution according to the vibration of thevibrator according to the first embodiment of the invention, by thefinite element method. FIG. 4A is a perspective view illustrating theheat distribution. FIG. 4B is an enlarged view of a D part in FIG. 4A.FIGS. 3A and 3B, and FIGS. 4A and 4B illustrate the temperature in awhite-colored part is high, and the temperature in a black-colored partis low. In addition, when the displacement direction of the vibration isreversed, the white-colored part becomes the black-colored part and thetemperature thereof is low, and the black-colored part becomes thewhite-colored part and the temperature thereof is high.

An upper electrode 120 of the vibrator in the related art as illustratedin FIG. 2A has a substantially right angled shape between each of theadjacent vibration portions 24, in the four vibration portions 24.However, in the upper electrode 20 of the vibrator according to thefirst embodiment as illustrated in FIG. 2B, each curved surface 40 isprovided between the four adjacent vibration portions 24. Regarding thevibrator which has two upper electrodes 120 and 20, an analysis of theheat distribution according to the vibration was performed by a finiteelement method. In addition, an analysis condition of the vibrator inthe finite element method is 14.29 μm in a width dimension W of thevibration portion 24, 10 μm in a length dimension L, 1.3 μm in a platethickness, and 1 μm in each of dimensions H1 and H2 of the supportingportion 26, in FIGS. 2A and 2B. In addition, a radius of curvature R ofthe curved surface 40 provided between the adjacent vibration portions24 is 2 μm in FIG. 2B.

In the vibrator in the related art in FIG. 2A, in a part in which theadjacent vibration portions 24 are in contact with each other which issubstantially in contact at a narrow interval between an area where awhite color temperature is high and an area where a black colortemperature is low, the Q value was 257,000, according to FIGS. 3A and3B which are analysis results. With respect to this, in the vibratoraccording to the first embodiment in FIG. 2B, in a part where theadjacent vibration portions 24 are in contact with each of the curvedsurfaces 40, the curved surface 40 is separated to be pinched betweenthe area where the white color temperature is high and the area wherethe black color temperature is low, and the Q value was 298,000,according to FIGS. 4A and 4B which are analysis results. According tothe result, when the area where the temperature is high and the areawhere the temperature is low are in contact, the Q value decreases bythe amount of thermoelastic damping generated by the heat conductiontherebetween. However, when the curved surface 40 was provided betweenthe adjacent vibration portions 24, it was identified that it ispossible to separate the area where the temperature is high and the areawhere the temperature is low, to reduce the thermoelastic damping as theheat conduction is unlikely to occur, and to reduce the deterioration ofthe Q value.

Therefore, by providing the curved surface 40 between the adjacentvibration portions 24, it is possible to keep apart the interval of theheat sources which generate the thermoelastic damping generated betweenthe adjacent vibration portions 24 which causes the deterioration of theQ value in addition to the energy dissipation. For this reason, it ispossible to reduce the discharge (thermoelastic damping) of the heat dueto the heat conduction between the heat sources, and to obtain a MEMSvibrator 100 having a high Q value and a stable vibration characteristicor a desired vibration characteristic.

Manufacturing Method

Next, a manufacturing method of the vibrator (MEMS vibrator 100)according to the embodiment will be described. In addition, according tothe description, the same configuration location described above willuse the same reference numerals and the repeating description thereofwill be omitted.

FIGS. 5A to 5F and FIGS. 6G to 6K are flow charts illustrating themanufacturing process of the MEMS vibrator 100 in order. States of theMEMS vibrator 100 in each process will be illustrated in thecross-sectional view taken along line A-A in FIG. 1A.

FIG. 5A: The substrate 1 is prepared and the oxide film 2 is stacked onthe main surface. The oxide film 2 is formed by a general localoxidation of silicon (LOCOS) as an element separation layer in asemiconductor process as a suitable example, but may be an oxide filmaccording to generation of the semiconductor process, for example,according to a shallow trench isolation (STI) method.

Next, the nitride film 3 is stacked as an insulating layer. Siliconnitride (Si₃N₄) forms the nitride film 3 by a low pressure chemicalvapor deposition (LPCVD). The nitride film 3 has a resistance withrespect to buffered hydrogen fluoride as an etchant which is used at atime of release etching of a sacrificing layer 8 (refer to FIG. 6G)which will be described later, and functions as an etching stopper.

FIGS. 5B and 5C: Then, as a first layer forming process, first of all,the first conductor layer 4 is stacked on the nitride film 3. The firstconductor layer 4 is a polysilicon layer which is configured to have thelower electrode 10 (first lower electrode 11, second lower electrode12), the wirings 11 a and 12 a (refer to FIG. 1A), or the like, and hasa predetermined conductivity by injecting ions, such as boron (B) orphosphorus (P) after the stacking. Next, by coating a resist 7 on thefirst conductor layer 4 and patterning by photolithography, the firstlower electrode 11, the second lower electrode 12, and the wirings 11 aand 12 a are formed. In the first layer forming process, when thesubstrate 1 is viewed from a planar view after a third layer formingprocess, the lower electrode 10 is formed in advance to be overlappedwith the upper electrode 20, in other words, the first lower electrode11 and the second lower electrode 12 are formed.

FIG. 5D: Next, as a second layer forming process, the second conductorlayer 5 is stacked to cover the lower electrode 10 and the wirings 11 aand 12 a. The second conductor layer 5 is a polysilicon layer whichconstitutes the supporting portion 26, and has the predeterminedconductivity by injecting ions, such as boron (B) or phosphorus (P)after the stacking.

FIGS. 5E and 5F: Next, the resist 7 is coated on the second conductorlayer 5, and by patterning by photolithography, the supporting portion26 is formed. The supporting portion 26 forms a gap in the first lowerelectrode 11, the second lower electrode 12, and the upper electrode 20,separates the upper electrode 20, and is formed to be overlapped in thecenter part of the second lower electrode 12.

FIGS. 6G and 6H: Next, a sacrificing layer 8 is stacked to cover thelower electrode 10, the wirings 11 a and 12 a, and the supportingportion 26. The sacrificing layer 8 forms the gap between the firstlower electrode 11 and the second lower electrode 12, and the upperelectrode 20, is a sacrificing layer for separating the upper electrode20, and forms a film using the chemical vapor deposition (CVD) method.On the stacked sacrificing layer 8, an unevenness caused by a stepdifference of the patterned first lower electrode 11 or second lowerelectrode 12 appears. Then, the resist 7 is coated on the sacrificinglayer 8, and the sacrificing layer 8 on the supporting portion 26 isremoved after the patterning by photolithography.

FIGS. 6I and 6J: Next, as the third layer forming process, first of all,the third conductor layer 6 is stacked to cover the sacrificing layer 8and the supporting portion 26. The third conductor layer 6 is apolysilicon layer which is the same as the first conductor layer 4 orthe second conductor layer 5, and has the predetermined conductivity byinjecting ions, such as boron (B) or phosphorus (P) after the stacking.After that, by patterning by photolithography, the upper electrode 20(base portion 22, vibration portion 24) is formed. As illustrated inFIG. 1A, as an electrode which has an area that overlaps the first lowerelectrode 11 and the second lower electrode 12 when the substrate 1 isviewed from a planar view, the upper electrode 20 is formed in a shapesuch that the vibration portions 24 extend in a radial shape from thebase portion 22 of the center of the upper electrode 20.

FIG. 6K: Next, by bleaching the substrate 1 by the etchant (bufferedhydrogen fluoride) and etching-removing (release etching) thesacrificing layer 8, the gap between the first lower electrode 11 andthe second lower electrode 12, and the upper electrode 20 is formed, andthe upper electrode 20 is separated.

According to the description above, the MEMS vibrator 100 is formed.

In addition, it is preferable that the MEMS vibrator 100 is disposed ina cavity portion which is sealed in a decompression state. For thisreason, in manufacturing the MEMS vibrator 100, the sacrificing layerfor forming the cavity portion, a side wall portion which surrounds thesacrificing layer, a sealing layer which forms a lid of the cavityportion, or the like, are formed to be combined, but the descriptionthereof is omitted here.

In addition, the invention is not limited to the above-describedembodiment, and various modifications or improvements are possible to beadded to the above-described embodiment. Modification examples will bedescribed hereinafter. Here, the same configuration part as theabove-described embodiment will use the same reference numerals and therepeated description thereof will be omitted.

Modification Example 1

FIGS. 7A and 7B are plan views illustrating a vibrator (MEMS vibrator100) and an example of a variation of the upper electrode provided withthe curved surface 40 between the adjacent vibration portions 24according to Modification Example 1.

As illustrated in FIG. 7A, in the upper electrode 20 a according toModification Example 1, a width dimension of an tip end provided with agradually decreasing portion 30 in a direction opposite to the baseportion 22 side of the vibration portion 24 a is smaller than a widthdimension of a root portion 28 (curved surface 40) side provided with acurvature portion which is in contact with the base portion 22. In otherwords, the vibration portion 24 a, in which the width of the tip endportion is smaller than that of the base portion 22 side end portion, isprovided. According to the configuration, in a part in which the rootportion 28 provided with the curvature portion and the graduallydecreasing portion 30 in which the width becomes smaller toward the tipend side are connected to each other, the stress due to the vibration isconcentrated. For this reason, since the thermoelastic damping generatedaccording to the concentration of the stress can be reduced, it ispossible to provide a MEMS vibrator 100 having a high Q value.

As illustrated in FIG. 7B, in the upper electrode 20 b, according toModification Example 1, a supporting portion 26 b provided with a fixingportion 32 at the end portion in a direction opposite to the baseportion 22, is connected to a part of the curved surface 40 between theadjacent vibration portions 24 which becomes the nodal point. Accordingto the configuration, it is possible to fix the fixing portion 32 ontothe substrate, and to keep the vibration portion 24 of the upperelectrode 20 b separate from the substrate with the supporting portion26 b. In addition, by connecting the supporting portion 26 b between theadjacent vibration portions 24 which becomes the nodal point, it ispossible to reduce the deterioration of the Q value caused by the energydissipation, and to provide a MEMS vibrator 100 having a high Q value.In addition, as there are plural supporting portions 26 b, it ispossible to improve impact resistance and to provide a MEMS vibrator 100having an excellent impact resistance and a high Q value.

Modification Example 2

Next, FIGS. 8A to 8D are plan views illustrating a vibrator (MEMSvibrator 100) and an example of a variation of the upper electrode ofthe vibrator according to modification example 2.

In the above-described embodiment, as illustrated in FIG. 1A, the upperelectrode 20 is described as the upper electrode 20 which forms a crossshape with the four vibration portions 24 that extend from the baseportion 22. However, the configuration is not limited thereto. Thenumber of vibration portions 24 may be an even number or an odd number,and four or more upper electrodes 20 may be formed.

FIG. 8A is an example illustrating an upper electrode 20 c configured ina disc shape. When the vibration occurs such that phases of thevibration of vibration portions 24 c adjacent to each other arereversed, it is possible to provide a MEMS vibrator 100 having a high Qvalue in which the deterioration of the vibration efficiency and theenergy dissipation are suppressed.

FIG. 8B is an example illustrating an upper electrode 20 d having sixvibration portions 24 d. When the vibration occurs such that phases ofthe vibration of the vibration portions 24 d adjacent to each other arereversed, it is possible to provide a MEMS vibrator 100 having a high Qvalue in which the deterioration of the vibration efficiency and theenergy dissipation are suppressed.

FIG. 8C is an example illustrating an upper electrode 20 e having eightvibration portions 24 e. When the vibration occurs such that phases ofthe vibration of the vibration portions 24 e adjacent to each other arereversed, or when two vibration portions 24 e adjacent to each othervibrate as one group in the same phase as illustrated in FIG. 8C, andthe vibration occurs such that the phases of the vibration of theadjacent groups are reversed, it is possible to provide a MEMS vibrator100 having a high Q value in which the deterioration of the vibrationefficiency and the energy dissipation are suppressed.

FIG. 8D is an example illustrating an upper electrode 20 f having fivevibration portions 24 f 1 to 24 f 3. A vibration portion 24 f 2 and twovibration portions 24 f 3 which pinch the base portion 22 at a facingposition have different lengths (length in a width direction) of adirection which intersects a direction that extends from the baseportion 22, and the length of a width direction of the vibration portion24 f 2 is relatively longer than the length of a width direction of thetwo vibration portions 24 f 3. This is done to balance the vibration ofthe entire upper electrode 20 f in which the base portion 22 and thevibration portions 24 f 1, 24 f 2, and 24 f 3 are integrated in a nodalpoint. By this configuration, even when the total number of thevibration portions 24 f 1, 24 f 2, and 24 f 3 is an odd number, it ispossible to provide a MEMS vibrator 100 having a high Q value in whichthe deterioration of the vibration efficiency and the energy dissipationare suppressed.

Second Embodiment

Next, a vibrator according to a second embodiment of the invention willbe described with reference to FIG. 9.

FIG. 9 is a plan view of the upper electrode of the vibrator accordingto the second embodiment of the invention.

Hereinafter, an upper electrode 20 g of the vibrator according to thesecond embodiment will be described, focusing on points different fromthe above-described first embodiment. In addition, in a similarconfiguration, the same reference numerals are used, and the descriptionof similar items will be omitted.

As illustrated in FIG. 9, the upper electrode 20 g according to thesecond embodiment is substantially similar to the first embodimentexcept that a convex portion 42 is provided between the adjacentvibration portions 24. By providing the convex portion 42 between theadjacent vibration portions 24, similarly to a case where the curvedsurface 40 is provided in the first embodiment, it is possible to keepapart the interval between the generated heat resources. For thisreason, it is possible to reduce the discharge (thermoelastic damping)of the heat due to the heat conduction between the heat sources, and toobtain a MEMS vibrator 100 having a high Q value and a stable vibrationcharacteristic or a desired vibration characteristic.

Above, in the vibrator according to the first embodiment in FIG. 1A, thevibrator according to Modification Example 1 in FIG. 7A, the vibratoraccording to Modification Example 2 in FIGS. 8A to 8D, and the vibratoraccording to the second embodiment in FIG. 9, the shape of thesupporting portion 26 provided in the center part of the base portion 22is configured to be rectangular. However, the configuration is notlimited thereto, and may be a polygon, a circle, or a cross. Inaddition, one supporting portion 26 is provided, but the invention isnot limited thereto, and a plurality of supporting portions 26 may beprovided.

Oscillator

Next, an oscillator 200 which employs the MEMS vibrator 100 as anoscillator according to an embodiment of the invention will be describedbased on FIG. 10.

FIG. 10 is a schematic view illustrating a configuration example of anoscillator provided with the MEMS vibrator 100 according to anembodiment of the invention. The oscillator 200 is configured to havethe MEMS vibrator 100, a bias circuit 70, and amplifiers 71 and 72.

The bias circuit 70 is a circuit which is connected to the wirings 11 aand 12 a of the MEMS vibrator 100, and applies the AC voltage in which apredetermined electric potential is biased in the MEMS vibrator 100.

The amplifier 71 is a feedback amplifier which is connected to thewirings 11 a and 12 a of the MEMS vibrator 100, in parallel with thebias circuit 70. By performing the feedback amplification, the MEMSvibrator 100 is configured as the oscillator 200.

The amplifier 72 is a buffer amplifier which outputs an oscillationwaveform.

According to the embodiment, as the MEMS vibrator 100 having a high Qvalue is provided as the oscillator 200, it is possible to provide anoscillator 200 having higher functionality.

Electronic Device

Next, an electronic device which employs the MEMS vibrator 100 as anelectronic component according to an embodiment of the invention will bedescribed based on FIGS. 11A and 11B, and FIG. 12.

FIG. 11A is a schematic perspective view illustrating a configuration ofa mobile-type (or note-type) personal computer as the electronic deviceprovided with the electronic component according to the embodiment ofthe invention. In the drawing, a personal computer 1100 is configured tohave a main body portion 1104 provided with a keyboard 1102 and adisplay unit 1106 provided with a display portion 1000. The display unit1106 is supported to be rotatable via a hinge structure portion withrespect to the main body portion 1104. In the personal computer 1100,the MEMS vibrator 100 as the electronic component which functions as afilter, a resonator, a reference clock, or the like is embedded.

FIG. 11B is a schematic perspective view illustrating a configuration ofa mobile phone (including PHS) as the electronic device provided withthe electronic component according to the embodiment of the invention.In the drawing, a mobile phone 1200 is provided with a plurality ofoperation buttons 1202, an ear piece 1204, and a mouth piece 1206. Thedisplay portion 1000 is disposed between the operation button 1202 andthe ear piece 1204. In the mobile phone 1200, the MEMS vibrator 100 asthe electronic component (timing device) which functions as the filter,the resonator, an angular velocity sensor, or the like is embedded.

FIG. 12 is a schematic perspective view illustrating a configuration ofa digital still camera as the electronic device provided with theelectronic component according to the embodiment of the invention. Inaddition, in the drawing, a connection with an outer device is alsosimply illustrated. A digital still camera 1300 performs photoelectricconversion of an optical image of a subject by a photographing element,such as a charged coupled device (CCD), and generates a photographingsignal (image signal).

On a rear surface of a case (body) 1302 in the digital still camera1300, the display portion 1000 is provided, and a display is performedbased on the photographing signal by the CCD. The display portion 1000functions as a finder which displays the subject as an electronic image.In addition, on a front surface side (back surface side in the drawing)of the case 1302, a light receiving unit 1304 including an optical lens(photographing optical system) or the CCD is provided.

When a photographer confirms a subject image displayed on the displayportion 1000 and pushes a shutter button 1306, the photographing signalof the CCD at that moment is sent and stored in a memory 1308. Inaddition, in the digital still camera 1300, on a side surface of thecase 1302, a video signal output terminal 1312 and a data communicationinput and output terminal 1314 are provided. As illustrated in thedrawing, a television monitor 1330 is connected to the video signaloutput terminal 1312, and a personal computer 1340 is connected to thedata communication input and output terminal 1314, as necessary,respectively. Furthermore, according to a predetermined operation, thephotographing signal stored in the memory 1308 is output to thetelevision monitor 1330 or the personal computer 1340. In the digitalstill camera 1300, the MEMS vibrator 100 is embedded as the electroniccomponent which functions as the filter, the resonator, the angularvelocity sensor, or the like.

As described above, as the vibrator (MEMS vibrator 100) having a high Qvalue is used as the electronic component, it is possible to provide anelectronic device having higher functionality.

In addition, the MEMS vibrator 100 as the electronic component accordingto the embodiment of the invention can be employed in the electronicdevice, such as an ink jet type discharging apparatus (for example, anink jet printer), a laptop type personal computer, a television, a videocamera, a car navigation apparatus, a pager, an electronic organizer(including an electronic organizer having a communication function), anelectronic dictionary, an electronic calculator, an electronic gamedevice, a work station, a video telephone, a television monitor forcrime prevention, an electronic binoculars, a POS terminal, a medicaldevice (for example, an electronic thermometer, a sphygmomanometer, ablood sugar meter, an electrocardiograph, an ultrasonic diagnosticequipment, and an electronic endoscopy), a fish finder, variousmeasurement apparatuses, meters (for example, meters of the vehicle, anaircraft, or a vessel) or a flight simulator, in addition to thepersonal computer (mobile type personal computer) in FIG. 11A, themobile phone in FIG. 11B, and the digital still camera in FIG. 12.

Moving Object

Next, a moving object which employs the MEMS vibrator 100 as thevibrator according to the embodiment of the invention will be describedbased on FIG. 13.

FIG. 13 is a schematic perspective view illustrating a vehicle 1400 asthe moving object provided with the MEMS vibrator 100. In the vehicle1400, a gyro sensor configured to have the MEMS vibrator 100 accordingto the invention of the invention is mounted. For example, asillustrated in FIG. 13, in the vehicle 1400 as the moving object, anelectronic control unit 1402, in which the gyro sensor that controls atire 1401 is embedded, is mounted. In addition, as another example, theMEMS vibrator 100 can be employed widely in an electronic control unit(ECU), such as a keyless entry, an immobilizer, a car navigation system,a car air conditioner, an anti-lock brake system (ABS), an air bag, atire pressure monitoring system (TPMS), an engine control, a batterymonitor of a hybrid vehicle or an electric vehicle, or a vehicle posturecontrol system.

As described above, as the vibrator (MEMS vibrator 100) having a high Qvalue is used as the moving object, it is possible to provide a movingobject having higher functionality.

As described above, the vibrator (MEMS vibrator 100), the oscillator200, the electronic device, and the moving object of the embodiment ofthe invention are described based on the embodiments illustrated in thedrawings. However, the invention is not limited thereto, and theconfiguration of each part can be replaced with an arbitraryconfiguration having similar functions. In addition, in the invention,another arbitrary component may be added. In addition, each of theabove-described embodiments may be suitably combined.

The entire disclosure of Japanese Patent Application No. 2013-214421,filed Oct. 15, 2013 is expressly incorporated by reference herein.

What is claimed is:
 1. A vibrator, comprising: a substrate; a baseportion which is disposed on the substrate; a plurality of vibrationportions which extend in directions different from each other from thebase portion; and a plurality of lower electrodes disposed on a surfaceof the substrate opposite the vibration portions and overlapped with theplurality of vibration portions and base portion in a plan view, whereinthe lower electrodes excite the vibration portions, and wherein a curvedsurface is provided between the adjacent vibration portions.
 2. Thevibrator according to claim 1, further comprising a supporting portionconnecting the substrate and the base portion and being connected to asurface of a side facing the substrate of the base portion.
 3. Thevibrator according to claim 2, wherein there are plural supportingportions.
 4. An oscillator, comprising: the vibrator according toclaim
 1. 5. An electronic device, comprising: the vibrator according toclaim
 1. 6. A moving object, comprising: the vibrator according to claim1.